Category Archives: astro

It’s a Skywatcher Stargate 500p Dobsonian truss-type telescope. The primary mirror is a full half-metre wide, it has a 2 metre focal length. It’s an absolute light bucket. It comes with a computerised goto drive, and it takes me less than about 10 min to set it up and have it running.

It came in 4 large boxes, with a shipping weight of about 95 kg.

I updated my eyepiece collection to suit the f/3.94 focal ration, with a Paracorr, a few Ethos 100-degree eyepieces, and a widest-field Explore Scientific 25mm 100 degree eyepiece. I now understand exactly why people got for the green eyepieces when they can..

The views through this scope are, not surprisingly for a 20″ scope, absolutely spectacular. Theoretically from a dark sky this scope should get visually down to mag 16.2 or so. Trying my hand at some Electronically Assisted Astronomy with the ASI224MC I got a nice view of the core of M42, about 2 min of stacking of 1/8th second (!) exposures and managing to capture some of the proplyds (nascent star solar systems):

Using the larger 4/3rds OSC CMOS camera that I also got recently (an ASI294MC-Pro) I stacked 2 second subs for ~4 min to get this M1 Crab nebula with lots of detail and down to mag 18 stars:

After a while the conditions overhead deteriorated poorly to the point where I could not make out the shape of Leo and the Plough asterism was becoming invisible. I persisted with taking subs of M51 to get this pic:

Overall – I’m *really* impressed with how this scope is performing for me. It’s a little bit of a bother to disassemble and reassemble and the heavy bits are rather awkward to try and get through a door – but they fit through a door. I’ve also found that I can strap the scope to a handcart and maneuver around the garden with ease, which bodes well for outreach with Astrosoc.

I have not yet had an opportunity to check a Moon or either of the large planets in the morning sky yet, really looking forwards to that..

I answered an ad on one of the astronomy forums I regularly peruse, where someone was getting rid of a badly water-damaged telescope. I figured it would make a nice project for myself so why not reply and see how much it was going to cost me.

A mate of mine picked up the telescope from the owner, and warned me that it appeared to be in relatively bad condition, so I was a little apprehensive.

When I collected the scope and paraphernalia from my friend, I recognised the scope as a Celestron CPC800 – a Schmidt-Cassegrain design with 8″ aperture and focal ration of f/10, with the computer control and GPS-based time and location finding. With the scope came the tripod and spreader bar, the standard 8×50 finder, a prism diagonal with 1.25″ visual back, an older NexStar handset, and the power cable with a generic wallwart adaptor. The tripod showed evidence of corrosion under the black paint on all of the non-chromed parts and a little surface rust on the bolts that hold the scope down. The ports on the fork base were showing heavy corrosion on the contact wires and a lot of green crud at the base of the ports, which did not bode well for the mechanicals at that point.. The tube was showing a lot of corrosion, with lots of the black paint paint on the front dell having been completely flaked off, and the metal underneath turning to a white flaky powder that had dusted all over the corrector plate. The primary mirror itself looked in reasonable condition actually, with a very light coating of dust but pretty much bright and untarnished in any way. The secondary was also appearing to be pristine

I took the scope home, and immediately started to disassemble, at 11pm, in my kitchen..

Attempting to power on the scope with power from the 12v lead acid battery that I use to power the AVX mount with, led to seeing a bright LED on the base lighting up, but absolutely no response from the handset. Knowing that the two AUX ports are parallel with the HC port, I tried the handset in the two AUX ports to have a response from the third port. The handset was alive at least. Motor errors 17 and 16, somewhat expected, showing a lack of communication with the motors. But, the motors would move but not stop. That was a really good sign! Maybe the scope could be resurrected without too much expense.

So, after a little research, I found I could replace the two circuit boards that are attached to the top plate of the fork base for a reasonable cost. The other PCBs around the scope appeared to be in good physical condition at least, dry and free from obvious corrosion. The testing of those would require the two boards in the base to be correct, as it appeared that the errors 17 and 16 were as a result of low power, mostly due to corrosion raising resistances and allowing current leakage between wires.

The replacement boards arrived, (many thanks to Stephen in Ktec Telescopes for a quick turnaround), and the installation of these was trivial enough. The smoke test was passed – nothing let out the magic smoke when power was applied! The handset powered up without issue, and the motors appeared to work perfectly on all axes at all speeds tested. I parked the scope outside on a paving stone in the lawn, and left it powered on for ~30 minutes to see if it could pick up a GPS fix. It did in fact pick up a GPS fix, one that was correct for both time and location, so I knew now that the electrics and electronics were now in fairly good condition.

I connected the serial port from one of my Dell SFF pcs to the handset, and powered on the scope. Using the HCUpdate and MCUpdate programs from the Celestron website, I was able to flash the current firmware on the handset. The motor controllers were at current levels anyway, not that surprising as the current version is unchanged since ~2011 or so.

Now on to the optics and tube. The corrosion on the tube front cell was such that the little steel screws holding on the corrector plate had bound tightly to the aluminium alloy body of the cell. Three screws were not bound and came away with a little bit of brute force and ignorance. One screw simply sheared off under the head, another two would not budge and have needed to be drilled off to allow the corrector plate to be removed for cleaning. The secondary is a Fastar-compatible and could be removed easily while I was trying all of this. It’s rather nerve-wracking to use spinning HSS steel bits that close to the corrector plate.. Eventually I managed to get the black plastic ring with the white writing off, and I could remove the corrector plate from the cell.

There was much brushing and cleaning of the cell as it was very flaky and dropping powder all of the time. I got all of the loose powder and pretty much all of the visible corrosion off, but I know I have another day of work to properly refurbish the cell. The screws and nuts holding the cell to the tube are bound solid in the aluminium cell – I managed to twist one of my screwdriver bits when trying to work it free so it was not a lack of torque at least.

The cleaning of the corrector plate was a fairly tedious process as there were significant marks in the anti-reflection coatings. Clean flowing water with a little dish soap and fingers, isopropanol and cottonwool, careful application of distilled water then to rinse. There are still some faint marks left but I expect that these are going to be pretty much invisible in general use.

The next step for me was to update the spare NexStar+ handset left over from my StarSense update that was performed on my AVX mount. Flashing it with the alt-az firmware via the Celestron CFM software meant that it was now suitable for the CPC mount. Testing the handset showed it to work exactly as was hoped, with the updated catalogues available for use, as well as the more familiar layout of the buttons and functions. Connection from the SkyFi box was also working perfectly.

Putting everything back together, cleaning all of the dust out of the base and re-lubricating the worm and wheels at the same time, I had a partial first light on a cloudy day. Using a Hubble Optics “artificial star” I could attempt a collimation across the length of Lily’s lawn. Using an 8mm eyepiece, and the working motor drives, I could get a pretty symmetrical set of in-focus diffraction rings. It really looks as though the optics are good enough to use!

First light was on a typically broken cloudy Irish evening. Two star align went okay, aligning the finderscope in the process. Given the weather conditions, double stars were the order of the day. Lots of pretty sights, Izar was cleanly split, the double-double Epsilon Lyrae was also cleanly split. Both were with very visible diffraction rings. Intra-focal and extra-focal were reasonable and will require a more comprehensive Roddier analysis in coming weeks.

EAA with the SCB-4000 camera was successful though the long focal length is a hamper. My 0.5x reducer is pretty crappy and gives teardrop aberrations halfway to the edge of view. I’ve got a 6.3 reducer in my hand that should help with the visual field, as I have a 18mm 82 degree eyepiece that should give a nice 1.15 degree FOV up from the 0.7 degree when at f/10, while still giving me an exit pupil of 0.75 with my 4.7mm. 275x is still not commonly usable in Ireland with the seeing we usually get here..

The plan is for this scope to be used by the UL Astronomy Society for member use and public outreach. I will be maintaining the scope and keeping possession of it when not actively used by the AstroSoc. It should mean more availability compared to the hoops needing jumping through to get the Physics Dept 10″ Meade LX10 out for use.

Black Friday / Cyber Monday. Lovely little words that mean decent deals on techie things, and an opportunity to get a few bits and pieces that I’ve been meaning to get for a while.

On the astronomy front, I’m ordering a Celestron AVX mount. After a year without a computerised GoTo system, I’ve been missing the ability to just select an object and have the scope slew to wherever that object was. Plus, I’ve got my low-light security camera all ready to do electronically-assisted astronomy, to get a look at all those little smudges of light.. So, I’m getting this mount to attach either of my two smaller scopes to. With the SCB-4000 camera and a portable screen, I’ll be able to get colour images in a few seconds, and I’ll be able to show those faint objects to other people as well. This mount should have decent tracking capabilities, enough that I should be able to take proper astrophotos again and fill out my portfolio of faint things. I’ll be on the lookout for a nice low f/ratio Newt for the video astronomy, and I’ll go quasar hunting..

I’ve picked up a SkyFi box and a cheap Amazon Fire 7 tablet to run SkySafari on, so that I can click on-screen and get the scope to move to where I’ve requested – wirelessly. I had to find another rom for the Fire tablet, removing all of the Amazon-only cruft from it and allowing the apps I’ve already paid for to run correctly on the tablet. The original OS on it prevents apps from contacting Google license servers, which stopped SkySafari from running. I’m planning on doing a completely wireless setup at some point, with wireless control of the camera and mount, which should make for easier setup and use when I’m out in the backyard. It’ll also mean that I can observe from inside when the scope is outside!

To the behemoth desktop computer I’ve added another 16Gb of ram for a total of 32. I should have no issues with running virtual machines for the thesis display now – not that I had much issue in the first place. Still, for a machine that’s 4 years old, it’s still ahead of the curve and above the average, still in the top 2% of systems according to the Steam hardware survey. I may yet add another 16Gb to restore the quad channel memory access that I had, as I now have 4x4Gb and 2x8Gb, and two free slots. I’m not looking forwards to having to hibernate this!

It was also an opportunity to try out one of the reshipping companies in the States, as there’s a new series of astronomy books being published, that will effectively become a modern Burnham’s Celestial Handbook. Amazon’s listing for the book didn’t ship to Ireland, so I trialled the sending of this to the reship company for further shipping, akin to the Parcel Motel idea. Turns out that the postage is x2 the cost of the book, and I’m not hugely happy with that, but I’ll have the book for cheaper than Amazon UK were selling it delivered.

The Galaxy S6 will be getting a nice waterproof case. I’ll have to look into sourcing a new gorilla glass screen for the phone, now that it will be protected again. Still kicking myself about having ordered the wrong model, and cracking the screen the day that the wrong model arrived! That will be a fun day fixing that, getting the heat gun out and replacing the outer glass screen.

I also managed to pick up a few Christmas present items, that I know will be appreciated.

It’s that time of the semester again when the assignments pile up (20%+10% for wk10, 10% for wk 11 and 2x 40% for wk 12) as well as the continuation of the thesis work, as well as just making sure that I’m on top of the standard study for the end of semester exams. Not the easiest in its own right – it’s why it is a Masters I suppose.

Add to that the 40 hours a week for the usual firefighting and the project work for my place of employment, and I have a lack of time to do anything..

With the good weather recently, I took a few hours to get out and take advantage of the exceptional seeing conditions to get some video captures of Mars and Saturn. I went through three batteries in the 600D on Tuesday night on Jupiter and the moon through the 4″ achromat, then Mars and Saturn through the 8″ newt. I’m still learning how to post-process properly so these can be considered a work in progress. I’m still doing something wrong, but I’ll figure it out eventually (after the Masters is done!):

Saturn:

Mars at 12 arsec diameter:

I’m at about 350kms on the road bike – I’ve found that cycling is good for the sanity sometimes, to clear the head when it’s overloaded with stuff..

The MR2 should be back on the road this month for the summer, once I replace the tyre that was slashed and get it re-taxed. It’ll be good to get the wind in the hair again, but petrol currently at 1.68/litre will be curtailing my driving in it a bit!

Everything is gearing up for the end of semester exams, during the first two weeks in May. It’ll be good to be finished and back to having weekends, to pursue the thesis work and studying for the I-Grade exam in maths in August. September will be getting the cisco certifications that I’m looking for. That’ll make a difference for my career path :)

So I’ve picked up a Coronado h-alpha PST scope second hand. I’ve managed to get the hang of attaching the canon to the little scope, and to get a half-decent picture of the h-alpha features on the sun, and the faint prominences down on the bottom right of this pic. The pic is a single frame pic with very light processing. I’ll have to get a good driven video capture and do some stacking in order to get more detail, but then again this is pretty good for through double-glazing at an angle.

I’m currently trying to retrofit the manfrotto head I picked up secondhand as well to the spare ETX tripod I have, to put this little scope onto.

Wow – another clear night where I could actually get out and get some stargazing done!

Seeing was reasonable, but not that good. I got a few videos of Jupiter, one of Mars, and a few of various bits of the moon. all to be processed at a later date. I tried a few 30 sec exposures of M42’s core – came out pretty well even accounting that I was using the 2x barlow to reach focus.. The trapezium was clearly resolved, as were the colours and Herschel’s “Mackerel Sky” pattern of the brightest part of the nebula. After waiting for Mars to clear the treetops to my southeast, I took off the 8″ from the LXD75 and put the Onyx onto the mount. I tried a few widefileds of M42 without much look, the streetlights were washing out the image. So I pointed high to the east, and aimed at M51.

I set the camera to no ISO noise reduction, and auto long exposure noise reduction was set on so that the camera would subtract a dark frame for each light taken. First impression was that I could get the cores of M51 and NGC 5195 and a tantalizing hint of spiral arms at 10 sec @ ISO 800. So I set it off to run out the battery at 1m exposures. I got 14 minutes of exposure, each one a bright orange :( But after downloading and working in IRIS, I got a reasonable image with mag 15 stars and mag 13.5 NGC galaxies in the image. I’m still working on it, but I’ll add it to this post when it’s done.

I got home from work at about 2am, so I brought out the grab’n’go scope (what a wonderful purchase that is turning out to be) and went for a wander to find somewhere dark.
I got a nice view of Saturn, with the banding on the planet, the shadow of the rings on the planet and the shadow of the planet on the rings, with the Cassini division visible most of the time.
Mars showed a very clear and obvious polar cap with a darker collar around it, as well as Syrtis Major and Utopia being visible. The phase was obvious – it wasn’t round!
I got some good views of some double stars, such as Algeiba, Izar and Porrima – all split cleanly at 125x though Izar wasn’t that easy.
M51 was quite well shown, easily seing the two galaxy disks and two nuclei, but no spiral structure.

Very nice short session that wound me down nicely from the evening’s work, and these quick grabs of suitable stargazing time have really made me thankful that I got the 80mm Onyx and the alt-az mount. Setup is minimal and the cooldown isn’t a big issue compared to the Newts.

Weather: 3-6 degrees, very broken light high altitude cloud, intermittent alto cumulus. There was a little local haze as well. Seeing was moderate to good, I could make out the Airy disks most of the time, as well as the first and second rings some of the time.

I set up the scope at sundown to give it a chance to temperature equalise, not that it needed much. Keeping the scope locked up in the shed really makes a difference to the visuals as there is a lack of tube thermals or boundary layer on the mirror.

After it got dark and I had 3-star aligned, I opened up the Collins Atlas of the Night Sky and I started trawling through the constellations, looking at each listed double star or deep space object.

Highlights include Gamma Sextantis seperated cleanly at ~1.0″ seperation, seeing the dust lanes in M64 and M104, locating and identifying each of the Messier galaxies in the Virgo cluster. Mag 11 galaxies were very difficult to see, M97 was just barely visible, M51 didn’t show the spiral arms only the dual cores and a very faint disk. NGC2419 was a possible as well, I’ll have to revisit that one.

Saturn was impressive as always, with four satellites clearly visible and I wasn;t sure if I saw Enceladus or not. I had trouble seeing the Cassini division as the seeing had deteriorated with large tremors rising off a nearby neighbours roof. As for the dragon storm, I could see a darker band across the southern hemisphere with tantalising hints of detail within it. I didn’t see a brighter portion at all.

I think I’ll have to start doing planned sessions where I have a list of items that I’ll take a look at, and a longterm plan is to view each of the double stars and the DSOs that are listed in Burnham’s handbook, and I’ll have to start taking better notes as well.

I parked the scope and packed up at about one o’clock, happy after an evening’s viewing that turned out to be more rewarding that the conditions would have led me to believe.

For once, it looked as though there was going to be some clear weather to get some stargazing done, and a proper first light for the 6″. The forecast was for some heavy showers so I had to keep a weather eye out in case I had to move in a hurry as I’m still working off main power until I figure a proper battery connection. The plan was to whistlestop on the sights, checking the GoTo and working between the clouds that were scudding across.

Around sunset, I decided to properly focus the polarscope as I messed that one up in my first attempts to use the mount indoors. This meant I had to realign the polarscope so I did a better job on that. I also got replacement cell batteries for the reticle illuminator and this makes a world of difference to polar aligning!. I levelled the tripod and marked the feet tips on the tarmac, to help with any daytime setup. After using the Polaris-Kochab Clock trick, I centered Polaris in the little circle and did a 3-star alignment. The handset tells me I’m less than 5′ from the pole. Not too bad a start!

I tried the “Best of Tonight” guide but that appeared to get a bit confused if a meridian flip was involved, so I went manually searching for targets.

M8 Lagoon Nebula. The first impressions of this were poorer than my 15×70 views recently, until I tried the UHC and OIII filters – took the nebula right out of the horizon haze, and made it clearly visible.

M20 Trifid Nebula. This was almost invisible, only really locatable with the multiple central star.

M22. Hazy and suffering from atmospheric extinction, but resolved and quite pretty. Oh to live further south to see these sights without peering through atmospheric murk!

103/P Hartley. The Autostar’s guess for the position was wrong, so I got the coords from heavens-above, typed in to the digital setting circles mode and there it was dead centre. Not easy, but visible with direct vision. Small and concentrating towards the nucleus.

Jupiter. The seeing was *terrible* with obvious rivers and waves of turbulent air rushing over the planet, distorting the limb and mushing up the cloud features. I could make out some features in the belts but it really was not easy.

All in all, a worthy 2 hours spent slewing and identifying, even though I didn’t spend a lot of time actually looking at things and I had to pick up and run with a large heavy rainshower that came in. Yes, the weather in this country sucks for astronomy.

I have been perusing the auction sites and the online classifieds over the past few months to keep an eye out if my bike showed up there. Recently I came across an LX75-N6-AT for sale there for a low price, with a problematic battery connection. I called up, called over and I examined this scope and mount, checked it out and I bought it. I had verified that the motors and the Autostar were functional with the use of a wallwart to provide the required DC power

I took it home and I knew that there was some backlash in both axes of the polar mount and that there was some collimation required as well, so out came the tools and off came the motor housings andaway went the backlash. Collimation was easy with the short length of the tube and the use of the combination cheshire tool that I got last year. Aligning the polar scope took a bit of time, and it is pretty much dead on now.

First light was Thursday night last week, chasing sucker holes in the cloud trying to polar-align, and to get guidestars to 3-star align the Autostar. Managed to get it aligned and operational, and then it was off to Jupiter. It’s interesting to note how much easier it is to observe fine details on Jupiter when it isn’t dancing around as it was in the ETX70 I also have. There were details in the belts that I wasn’t expecting to see, and I could differentiate that the moons of Jupiter were discs and not point sources as the nearby stars were. It was pretty amazing to be honest. The overall optical quality is better than I had anticipated and the inside/outside of focus tar test shows a little undercorrection, but the effect of this on a 6″ is minimal. In-focus, there are clear Airy disks with a first-order diffraction ring about as bright as expected from a scope with this level of central obstruction, and hints of the second order ring were seen as well.

Contrast is good, but I think that there may be a need for baffling and flocking to get the best performance from this scope, and I think that I will try to remove the mirror clips as these do affect the view. I’ll be on the lookout for a decent 6″ spider to replace the cast aluminium slabs that currently support the secondary. I found that I cannot reach focus with the webcam when using the 1.25″ adapter, so I’ll have to locate a 2″ to 1.25″ and then I’ll have no problems, and then I’ll start to get some decent Jupiter images ;)